Heat radiation apparatus, phase-change cooling apparatus including the same, and method for radiating heat

ABSTRACT

It is impossible, in a phase-change cooling apparatus in which a refrigerant flows in a gas-liquid two-phase state, to enhance cooling capacity sufficiently even though a heat-radiating region is enlarged; therefore, a heat radiation apparatus according to an exemplary aspect of the present invention includes gas-phase refrigerant diffusion means into which a refrigerant in a gas-liquid two-phase state flowing, the gas-phase refrigerant diffusion means being filled with a gas-phase refrigerant included in the refrigerant in the gas-liquid two-phase state; heat-radiating means including a first header, a second header, and a plurality of heat-radiating pipes connecting the first header to the second header, the gas-phase refrigerant flowing through the plurality of heat-radiating pipes; and gas-phase-side connection means for connecting the gas-phase refrigerant diffusion means to the first header, the gas-phase refrigerant flowing in the gas-phase-side connection means.

TECHNICAL FIELD

The present invention relates to heat radiation apparatuses, phase-change cooling apparatuses including the heat radiation apparatuses, and methods for radiating heat and, in particular, to a heat radiation apparatus, a phase-change cooling apparatus including the heat radiation apparatus, and a method for radiating heat that are used for cooling an electronic device or the like.

BACKGROUND ART

In recent years, with miniaturization and enhanced performance of an electronic device, the amount of heat generation and the heat generation density of the electronic device have been increasing. In order to cool such an electronic device or the like efficiently, it is necessary to adopt a cooling system having high cooling capacity. A phase-change cooling system using phase change of a refrigerant has attracted attention as one of the cooling systems having high cooling capacity.

In a cooling apparatus (phase-change cooling apparatus) by the phase-change cooling system, a refrigerant having received heat in a heat receiving section boils (vaporizes), becomes a gas-liquid two-phase flow, and then flows into a heat radiating section. The gas-phase refrigerant condenses and radiates heat in the heat radiating section; consequently, the heat is transported. In this case, if a liquid-phase refrigerant included in the gas-liquid two-phase flow directly enters a heat-radiating tube constituting the heat radiating section, the heat-radiating tube is blocked in the vicinity of an inlet port, which inhibits the gas-phase refrigerant from entering. As a result, there has been the problem that the refrigerant becomes unable to circulate satisfactorily.

One example of techniques to solve the problem is described in Patent Literature 1. A phase-change cooling apparatus (boiling cooling apparatus) described in Patent Literature 1 includes a refrigerant tank in which to pool a liquid refrigerant, and a heat radiator to liquefy the refrigerant vapor that boils having received heat of a heating element in the refrigerant tank by heat exchange with external fluid (air, for example).

The heat radiator includes a vapor-side header into which the refrigerant vapor having boiled by receiving heat of the heating element in the refrigerant tank flows, a core section composed of a heat-radiating tube and a heat-radiating fin, and a liquid-side header into which condensate liquid having liquefied in the core section flows. The heat-radiating tube connects the vapor-side header to the liquid-side header. One end of the heat-radiating tube is disposed protruding into the vapor-side header from an inner wall surface of a header plate of the vapor-side header, which forms a gas-liquid separating structure.

The above-described configuration can prevent the liquid refrigerant from entering the heat-radiating tube even though the liquid refrigerant scattering with the refrigerant vapor from the refrigerant tank enters the vapor-side header, because the liquid refrigerant and the refrigerant vapor are separated from each other by the gas-liquid separating structure in the vapor-side header. As a result, it is said that the boiling cooling apparatus described in Patent Literature 1 can operate stably because only refrigerant vapor can enter the heat-radiating tube, and a refrigerant can circulate successfully between the refrigerant tank and the heat radiator.

CITATION LIST Patent Literature

[PTL 1] Japanese Unexamined Patent Application Publication No. 2000-156444 (paragraphs [0010] to [0022], FIG. 1)

SUMMARY OF INVENTION Technical Problem

As mentioned above, the related phase-change cooling apparatus (boiling cooling apparatus) described in Patent Literature 1 is configured to include the heat radiator in which one end of the heat-radiating tube is disposed protruding into the vapor-side header. The configuration prevents the gas-phase refrigerant from being filled sufficiently into an end of the vapor-side header even though a heat-radiating region is enlarged by increasing the heat-radiating tube in order to enhance cooling capacity, because a flow of the gas-phase refrigerant is prevented due to the protruding end of the heat-radiating tube. As a result, there has been the problem that it is impossible to enhance cooling capacity of the related phase-change cooling apparatus.

As mentioned above, there has been the problem that it is impossible, in a phase-change cooling apparatus in which a refrigerant flows in a gas-liquid two-phase state, to enhance cooling capacity sufficiently even though a heat-radiating region is enlarged.

The object of the present invention is to provide a heat radiation apparatus, a phase-change cooling apparatus including the heat radiation apparatus, and a method for radiating heat that solve the above-mentioned problem that it is impossible, in a phase-change cooling apparatus in which a refrigerant flows in a gas-liquid two-phase state, to enhance cooling capacity sufficiently even though a heat-radiating region is enlarged.

Solution to Problem

A heat radiation apparatus according to an exemplary aspect of the present invention includes gas-phase refrigerant diffusion means into which a refrigerant in a gas-liquid two-phase state flowing, the gas-phase refrigerant diffusion means being filled with a gas-phase refrigerant included in the refrigerant in the gas-liquid two-phase state; heat-radiating means including a first header, a second header, and a plurality of heat-radiating pipes connecting the first header to the second header, the gas-phase refrigerant flowing through the plurality of heat-radiating pipes; and gas-phase-side connection means for connecting the gas-phase refrigerant diffusion means to the first header, the gas-phase refrigerant flowing in the gas-phase-side connection means.

A method for radiating heat according to an exemplary aspect of the present invention includes receiving a refrigerant in a gas-liquid two-phase state, and generating a diffused gas-phase refrigerant by uniformly diffusing a gas-phase refrigerant included in the refrigerant in the gas-liquid two-phase state; generating a plurality of gas-phase refrigerant flows by making the diffused gas-phase refrigerant branch; and condensing and liquefying each of the plurality of gas-phase refrigerant flows.

Advantageous Effects of Invention

According to the heat radiation apparatus, the phase-change cooling apparatus including the heat radiation apparatus, and the method for radiating heat of the present invention, it is possible to enhance cooling capacity sufficiently by enlarging a heat-radiating region even though a phase-change cooling system in which a refrigerant flows in a gas-liquid two-phase state is used.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view illustrating a configuration of a heat radiation apparatus according to a first example embodiment of the present invention.

FIG. 2 is an elevation view illustrating a configuration of a heat radiating section included in the heat radiation apparatus according to the first example embodiment of the present invention.

FIG. 3 is a sectional view illustrating a configuration of a heat radiating section included in the heat radiation apparatus according to the first example embodiment of the present invention.

FIG. 4 is a sectional view illustrating another configuration of a heat radiation apparatus according to the first example embodiment of the present invention.

FIG. 5 is a sectional view illustrating a configuration of a heat radiation apparatus according to a second example embodiment of the present invention.

FIG. 6 is an elevation view illustrating another configuration of the heat radiation apparatus according to the second example embodiment of the present invention.

FIG. 7 is a schematic view illustrating a configuration of a phase-change cooling apparatus according to a third example embodiment of the present invention.

EXAMPLE EMBODIMENT

Example embodiments of the present invention will be described with reference to drawings below.

First Example Embodiment

FIG. 1 is a sectional view illustrating a configuration of a heat radiation apparatus 100 according to a first example embodiment of the present invention. The heat radiation apparatus 100 according to the present example embodiment includes a gas-phase refrigerant diffusion section 110, a heat radiating section 120, and a gas-phase-side connection 130. FIG. 2 illustrates an elevation view of the heat radiating section 120, and FIG. 3 illustrates a sectional view of the heat radiating section 120, respectively.

A refrigerant in a gas-liquid two-phase state flows into the gas-phase refrigerant diffusion section 110, which is filled with a gas-phase refrigerant included in the refrigerant in the gas-liquid two-phase state. The heat radiating section 120 includes a first header 121, a second header 122, and a plurality of heat-radiating pipes 123 connecting the first header 121 to the second header 122. The gas-phase refrigerant flows through the plurality of heat-radiating pipes 123. The gas-phase-side connection 130 connects the gas-phase refrigerant diffusion section 110 to the first header 121, which makes the gas-phase refrigerant flow.

The above-described configuration enables the gas-phase refrigerant included in the refrigerant in the gas-liquid two-phase state to diffuse within and fill the gas-phase refrigerant diffusion section 110, and then flow into the first header 121 constituting the heat radiating section 120 through the gas-phase-side connection 130. Consequently, the heat-radiating pipes 123 do not prevent the gas-phase refrigerant from flowing and diffusing even though a heat-radiating region is enlarged by increasing the number of heat-radiating pipes 123 in order to enhance cooling capacity. Therefore, according to the heat radiation apparatus 100 in the present example embodiment, it is possible to enhance cooling capacity sufficiently by enlarging a heat-radiating region even though a phase-change cooling system in which a refrigerant flows in a gas-liquid two-phase state is used.

The heat radiating section 120 is typically a parallel-flow-type heat radiator as illustrated in FIG. 2. That is to say, the heat radiating section 120 can have a configuration in which pipe-shaped headers are disposed at the top (a first header 121) and the bottom (a second header 122), and these headers are connected to each other through heat-radiating tubes (the heat-radiating pipes 123), for example. A fin 124 is formed on the surface of the heat-radiating tube (heat-radiating pipe 123), as illustrated in FIG. 2. This increases the surface area; accordingly, this enables the capability of radiating heat into air to improve. The sectional shape of the header may be cylindrical or square.

As illustrated in FIG. 3, the gas-phase-side connection 130 can be configured to connect the gas-phase refrigerant diffusion section 110 to a central region in a longitudinal direction of the first header 121. This minimizes the distance from the inflow position of the gas-phase refrigerant to the farther edge of the first header 121; therefore, the pressure loss of the gas-phase refrigerant is reduced, and the cooling efficiency can be improved.

As illustrated in FIG. 3, the heat-radiating pipe 123 can have a configuration in which a first end of the heat-radiating pipe 123 extends into the first header 121. That is to say, the upper header (first header 121) can be configured to have a large number of through holes and include the heat-radiating tubes (heat-radiating pipes 123) with fins on their outer periphery inserted to the vicinity of the center of the upper header. This makes the liquid-phase refrigerant LR included in the refrigerant in the gas-liquid two-phase state remain between the heat-radiating tubes (heat-radiating pipes 123); therefore, it becomes easy for the gas-phase refrigerant VR to flow.

As illustrated in FIG. 1, the gas-phase-side connection 130 includes a first pipe structure, and an extension of the central axis C1 of the first pipe structure can be located above a first end E1 of the heat-radiating pipe 123. In other words, the gas-phase-side connection 130 can be eccentrically connected so that the central axis C1 may be positioned above the central axis of the upper header (first header 121). In this case, with regard to the opening area in the connection of the gas-phase-side connection 130, the opening area above the central axis of the upper header becomes larger than the opening area below it. The above-described configuration makes it possible to prevent the liquid-phase refrigerant remaining between the heat-radiating tubes (heat-radiating pipes 123) from flowing back to the gas-phase-side connection 130.

FIG. 1 illustrates the gas-phase-side connection 130 that is connected to the first header 121 at a substantially right angle. It is not limited to this, but the central axis of the heat-radiating pipe 123 and the central axis C1 of the first pipe structure of the gas-phase-side connection 130 can have non-parallel relationship on the same plane. That is to say, the gas-phase-side connection 130 can be connected so as not to be parallel to the flow path direction (vertical direction) of the heat-radiating tube (heat-radiating pipe 123). Specifically, for example, as a heat radiation apparatus 101 illustrated in FIG. 4, the gas-phase refrigerant diffusion section 110 can be located obliquely upward on the first header 121, and the gas-phase-side connection 130 can be disposed obliquely with respect to the vertical direction. The above-described configuration makes it possible to avoid the direct inflow of the liquid-phase refrigerant included in the refrigerant in the gas-liquid two-phase state from the gas-phase-side connection 130 into the heat-radiating tube (heat-radiating pipe 123). This makes it possible to prevent the inflow of the gas-phase refrigerant into the heat-radiating tube (heat-radiating pipe 123) from being blocked by the liquid-phase refrigerant.

The gas-phase-side connection 130 and the gas-phase refrigerant diffusion section 110 or the upper header (first header 121) can be connected by brazing or welding.

Next, a method for radiating heat according to the present example embodiment will be described.

In the method for radiating heat according to the present example embodiment, first, a refrigerant in a gas-liquid two-phase state is received, and a diffused gas-phase refrigerant is generated by uniformly diffusing a gas-phase refrigerant included in the refrigerant in the gas-liquid two-phase state. Next, a plurality of gas-phase refrigerant flows are generated by making the diffused gas-phase refrigerant branch. Then each of the plurality of gas-phase refrigerant flows is condensed and liquefied. As described above, the gas-phase refrigerant is uniformly diffused and made to turn to the diffused gas-phase refrigerant, and then it is made to branch, which enables the pressure loss to decrease as compared with the case where a gas-phase refrigerant included in a refrigerant in a gas-liquid two-phase state is made to branch directly. In this case, the diffused gas-phase refrigerant can be made to branch so that the flow distribution of a plurality of gas-phase refrigerant flows may become symmetric. In this case, the maximum value of the pressure loss with respect to each of the plurality of gas-phase refrigerant flows can be decreased.

As mentioned above, according to the method for radiating heat of the present example embodiment, it is possible to enhance cooling capacity sufficiently even though a phase-change cooling system in which a refrigerant flows in a gas-liquid two-phase state is used.

Second Example Embodiment

Next, a second example embodiment of the present invention will be described. FIG. 5 illustrates a configuration of a heat radiation apparatus 200 according to the second example embodiment of the present invention.

The heat radiation apparatus 200 according to the present example embodiment includes a gas-phase refrigerant diffusion section 110, a heat radiating section 120, and a gas-phase-side connection 130. A refrigerant in a gas-liquid two-phase state flows into the gas-phase refrigerant diffusion section 110, which a gas-phase refrigerant included in the refrigerant in the gas-liquid two-phase state fills. The heat radiating section 120 includes a first header 121, a second header 122, and a plurality of heat-radiating pipes 123 connecting the first header 121 to the second header 122. The gas-phase refrigerant flows through the plurality of heat-radiating pipes 123. The gas-phase-side connection 130 connects the gas-phase refrigerant diffusion section 110 to the first header 121, which makes the gas-phase refrigerant flow. The configuration above is similar to the configuration of the heat radiation apparatus 100 according to the first example embodiment.

The heat radiation apparatus 200 according to the present example embodiment further includes a liquid-phase refrigerant transport section 210 and a liquid-phase-side connection 220, in addition to the above-described configuration. The liquid-phase refrigerant transport section 210 stores and transports a liquid-phase refrigerant having passed through the heat-radiating pipes 123. The liquid-phase-side connection 220 connects the liquid-phase refrigerant transport section 210 to the second header 122, which makes the liquid-phase refrigerant flow.

As illustrated in FIG. 5, the gas-phase refrigerant diffusion section 110 is located above the heat radiating section 120 and connected to the upper header (first header 121) through the gas-phase-side connection 130. In contrast, the liquid-phase refrigerant transport section 210 is located below the heat radiating section 120 and connected to a lower header (the second header 122) through the liquid-phase-side connection 220.

As illustrated in FIG. 5, the heat-radiating pipe 123 can have a configuration in which a second end E2 of the heat-radiating pipe 123 extends into the second header 122. The liquid-phase-side connection 220 includes a second pipe structure, and an extension of the central axis C2 of the second pipe structure can be located below the second end E2. In other words, the liquid-phase-side connection 220 can be eccentrically connected so that the central axis C2 may be positioned below the central axis of the lower header (the second header 122). In this case, with regard to the opening area in the connection of the liquid-phase-side connection 220, the opening area below the central axis of the lower header becomes larger than the opening area above it. The above-described configuration makes it easier for the liquid-phase refrigerant pooled in the lower header (the second header 122) to flow to the liquid-phase refrigerant transport section 210 through the liquid-phase-side connection 220.

The heat radiating section 120 may be configured to include a plurality of heat-radiating regions (heat radiators). That is to say, as illustrated in FIG. 6, a heat radiation apparatus 300 can be configured to include the gas-phase refrigerant diffusion section 110, the liquid-phase refrigerant transport section 210, the gas-phase-side connection 130, the liquid-phase-side connection 220, and the heat radiating section 120 including a plurality of heat-radiating regions (heat radiators) 320. Here, each of the heat-radiating regions (heat radiators) 320 includes a first header region (third header) 321 constituting a first header, a second header region (fourth header) 322 constituting a second header, and a plurality of heat-radiating pipes 323 connecting the first header region 321 to the second header region 322. The gas-phase refrigerant flows through the plurality of heat-radiating pipes 323. A parallel-flow-type heat exchanger can be typically used as each of the heat-radiating regions 320.

In this case, the gas-phase-side connection 130 is configured to include a plurality of gas-phase-side connection structures 330 each of which connects the gas-phase refrigerant diffusion section 110 to the first header region 321, which a gas-phase refrigerant flows through. The gas-phase-side connection structure 330 can be configured to connect the gas-phase refrigerant diffusion section 110 to a central region in a longitudinal direction of the first header region 321, respectively.

As illustrated in FIG. 6, the plurality of heat-radiating regions 320 are arranged in a longitudinal direction of each header region, and the gas-phase refrigerant diffusion section 110 can be disposed substantially parallel to the longitudinal direction of the header region.

In the heat radiation apparatus 300 described above, it is desirable for the cross-sectional area of the gas-phase refrigerant diffusion section 110 to be larger than the cross-sectional area of the first header region 321 because the gas-phase refrigerant diffusion section 110 has to supply the gas-phase refrigerant to the plurality of heat-radiating regions 320. It is also desirable, in order to reduce pressure loss, for the gas-phase-side connection structure 330 connecting the gas-phase refrigerant diffusion section 110 to each upper header (first header region 321) to include a pipe structure (pipe) with the cross-sectional area comparable to that of the upper header.

Next, the operations of the heat radiation apparatus 200 and the heat radiation apparatus 300 according to the present example embodiment will be described.

In phase-change cooling apparatuses, a refrigerant is transported in a state where gas-liquid two phases are mixed (a gas-liquid two-phase state). The reason is as follows. The liquid-phase refrigerant having received heat in a heat receiving apparatus (vaporization section) vaporizes and then flows into the gas-phase refrigerant diffusion section 110. In the heat receiving apparatus, not all the liquid-phase refrigerants phase-change to gas-phase refrigerants, but part of the refrigerants flows remaining in the liquid-phase refrigerant.

The refrigerant flowing in the gas-phase refrigerant diffusion section 110 branches and flows into each of the plurality of heat radiators (the heat radiating section 120, the heat-radiating regions 320) connected to the gas-phase refrigerant diffusion section 110. The refrigerant flows into the upper header (the first header 121, the first header region 321) of each heat radiator through the gas-phase-side connection structure 330.

The refrigerant in the gas-liquid two-phase state including the liquid-phase refrigerant having flowed into the upper header bumps against a wall surface of the upper header, and the liquid-phase refrigerant mixed with the gas-phase refrigerant drops. The reason is as follows. The liquid-phase refrigerant is larger in density than the gas-phase refrigerant; accordingly, it loses its momentum and drops under its own weight. In contrast, the gas-phase refrigerant is distributed in the upper part within the upper header because it is smaller in density than the liquid-phase refrigerant; accordingly, the gas-phase refrigerant loses a smaller amount of momentum compared to the liquid-phase refrigerant even though the gas-phase refrigerant bumps against the wall surface of the upper header. This makes the gas-phase refrigerant move along the wall surface of the upper header in the longitudinal direction of the upper header.

The gas-phase refrigerant having moved in the longitudinal direction of the upper header flows, from its opening, into each heat-radiating tube (the heat-radiating pipes 123, 323) connected to the upper header, and radiates the heat having received in the heat receiving apparatus, in the region where a fin is connected on the outside.

Here, as illustrated in FIG. 3, the heat-radiating tube (the heat-radiating pipe 123, 323) is inserted to the vicinity of the center of the upper header, which makes the liquid-phase refrigerant stored between the heat-radiating tubes in the upper header. Because the liquid-phase refrigerant stored between the heat-radiating tubes loses its fluidity in the longitudinal direction of the upper header due to the heat-radiating tubes, the gas-phase refrigerant mainly flows in the longitudinal direction of the upper header.

If a liquid-phase refrigerant is mixed in a gas-phase refrigerant, the gas-phase refrigerant is prevented from flowing because the liquid-phase refrigerant is larger in density than the gas-phase refrigerant. This makes it difficult to distribute the gas-phase refrigerant efficiently to each heat-radiating tube. However, the configurations of the heat radiation apparatus 200 and the heat radiation apparatus 300 according to the present example embodiment make it possible to increase the amount of gas-phase refrigerant that can move within the upper header. Consequently, the gas-phase refrigerant can be supplied more equally to each heat-radiating tube. This enables the cooling performance to improve.

In contrast, the liquid-phase refrigerant condensed in each heat-radiating tube drops due to the action of gravity, and flows into the lower header (the second header 122, the second header region 322). Not all the refrigerant flowing into the lower header is a liquid-phase refrigerant, but a gas-phase refrigerant is mixed in part of the refrigerant. Because the gas-phase refrigerant is smaller in density than the liquid-phase refrigerant, the gas-phase refrigerant remains in the upper part of the lower header. In this case, the heat radiation apparatus 200 and the heat radiation apparatus 300 according to the present example embodiment have a configuration in which the second end E2 of the heat-radiating tube (the heat-radiating pipe 123, 323) extends into the lower header (the second header 122, the second header region 322), as illustrated in FIG. 5. This makes the gas-phase refrigerant remain between the heat-radiating tubes. Because the heat-radiating tubes prevent the gas-phase refrigerant remaining between the heat-radiating tubes from flowing, it is limited to move in the longitudinal direction of the lower header.

Because the gas-phase refrigerant is smaller in density than the liquid-phase refrigerant, the gas-phase refrigerant is higher in flow velocity than the liquid-phase refrigerant, which sometimes prevents the liquid-phase refrigerant from flowing. In the heat radiation apparatus 200 and the heat radiation apparatus 300 according to the present example embodiment, however, it is possible to drain the liquid-phase refrigerant out into the liquid-phase refrigerant transport section 210 efficiently because the flow of the gas-phase refrigerant in the lower header is limited as mentioned above.

Thus, according to the heat radiation apparatus 200 and the heat radiation apparatus 300 of the present example embodiment, the gas-phase refrigerant is not prevented from flowing due to the mixed liquid-phase refrigerant, which makes it easier to distribute the gas-phase refrigerant equally to each heat-radiating tube. In addition, it is possible to drain the liquid-phase refrigerant condensed in the heat radiating section 120 out into the liquid-phase refrigerant transport section 210 efficiently without being blocked by the flow of the gas-phase refrigerant having flowed into the lower header remaining uncondensed. This makes it possible to improve the cooling performance of the heat radiation apparatuses 200 and 300.

As described above, according to the heat radiation apparatus 200 and the heat radiation apparatus 300 of the present example embodiment, it is possible to enhance cooling capacity sufficiently by enlarging a heat-radiating region even though a phase-change cooling system in which a refrigerant flows in a gas-liquid two-phase state is used.

Third Example Embodiment

Next, a third example embodiment of the present invention will be described. FIG. 7 schematically illustrates a configuration of a phase-change cooling apparatus 1000 according to the third example embodiment of the present invention.

The phase-change cooling apparatus 1000 according to the present example embodiment includes a heat radiation apparatus 1100, a heat receiving apparatus 1200, a first connection 1300, and a second connection 1400.

The heat radiation apparatus 1100 has a configuration similar to that of the heat radiation apparatus 200 or the heat radiation apparatus 300 according to the above-described second example embodiment, and includes the gas-phase refrigerant diffusion section 110, the heat radiating section 120, the gas-phase-side connection 130, the liquid-phase refrigerant transport section 210, and the liquid-phase-side connection 220. The heat radiation apparatus 1100 is typically a condenser that makes a gas-phase refrigerant condense and liquefy.

The heat receiving apparatus 1200 generates a refrigerant in a gas-liquid two-phase state by receiving heat from a cooling target. That is to say, the heat receiving apparatus 1200 includes a vaporizer that contains a refrigerant and generates a gas-liquid two-phase refrigerant by receiving heat.

The first connection 1300 connects the heat receiving apparatus 1200 to the gas-phase refrigerant diffusion section 110. The second connection 1400 connects the heat receiving apparatus 1200 to the liquid-phase refrigerant transport section 210.

The refrigerant in the gas-liquid two-phase state generated in the heat receiving apparatus 1200 passes through the first connection 1300, and then flows into the heat radiating section 120 through the gas-phase-side connection 130 from the gas-phase refrigerant diffusion section 110 in the heat radiation apparatus 1100. The liquid-phase refrigerant having condensed and liquefied in the heat radiating section 120 flows into the liquid-phase refrigerant transport section 210 through the liquid-phase-side connection 220, and flows back to the heat receiving apparatus 1200 through the second connection 1400. In this way, a phase-change cooling cycle is completed.

The phase-change cooling apparatus 1000 can be configured to include the heat receiving apparatus 1200 placed inside a building and the heat radiation apparatus 1100 placed outside the building, for example. Specifically, for example, the heat receiving apparatus 1200 is placed in a factory, a data center, or the like in order to receive heat generated in a server room or the like. The heat radiation apparatus 1100 is also placed in order to radiate heat received in the heat receiving apparatus 1100 to outside air.

The phase-change cooling apparatus 1000 is not limited to employing the phase-change cooling system with natural circulation of the refrigerant, but it can be also configured as a pump-circulation-type phase-change cooling apparatus by including a pump for refrigerant circulation in the second connection 1400.

The phase-change cooling apparatus 1000 according to the present example embodiment is configured to include the heat radiation apparatus 1100 configured similarly to the heat radiation apparatus 200 or the heat radiation apparatus 300 according to the second example embodiment. Therefore, as mentioned above, it is possible to enhance cooling capacity sufficiently by enlarging a heat-radiating region even though a phase-change cooling system in which a refrigerant flows in a gas-liquid two-phase state is used.

While the invention has been particularly shown and described with reference to example embodiments thereof, the invention is not limited to these embodiments. It will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the claims.

This application is based upon and claims the benefit of priority from Japanese patent application No. 2015-253988, filed on Dec. 25, 2015, the disclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST

-   100, 101, 200, 300 Heat radiation apparatus -   110 Gas-phase refrigerant diffusion section -   120 Heat radiating section -   121 First header -   122 Second header -   123, 323 Heat-radiating pipe -   124 Fin -   130 Gas-phase-side connection -   210 Liquid-phase refrigerant transport section -   220 Liquid-phase-side connection -   320 Heat-radiating region -   321 First header region -   322 Second header region -   330 Gas-phase-side connection structure -   1000 Phase-change cooling apparatus -   1100 Heat radiation apparatus -   1200 Heat receiving apparatus -   1300 First connection -   1400 Second connection 

What is claimed is:
 1. A heat radiation apparatus, comprising: a gas-phase refrigerant diffusion section into which a refrigerant in a gas-liquid two-phase state flows, the gas-phase refrigerant diffusion section being filled with a gas-phase refrigerant included in the refrigerant in the gas-liquid two-phase state; a heat-radiating section including a first header, a second header, and a plurality of heat-radiating pipes connecting the first header to the second header, the gas-phase refrigerant flowing through the plurality of heat-radiating pipes; and a gas-phase-side connection section configured to connect the gas-phase refrigerant diffusion section to the first header, the gas-phase refrigerant flowing in the gas-phase-side connection section.
 2. The heat radiation apparatus according to claim 1, wherein the gas-phase-side connection section connects the gas-phase refrigerant diffusion section to a central region in a longitudinal direction of the first header.
 3. The heat radiation apparatus according to claim 1, wherein a first end of the heat-radiating pipe extends into the first header, the gas-phase-side connection section includes a first pipe structure, and an extension of a central axis of the first pipe structure is located above the first end.
 4. The heat radiation apparatus according to claim 1, wherein the gas-phase-side connection section includes a first pipe structure, and a central axis of the heat-radiating pipe and a central axis of the first pipe structure have non-parallel relationship on a same plane.
 5. The heat radiation apparatus according to claim 1, wherein the heat-radiating section includes a plurality of heat radiators, each of the plurality of heat radiators includes a third header constituting the first header, a fourth header constituting the second header, and the plurality of heat-radiating pipes connecting the third header to the fourth header, and the gas-phase refrigerant flows through the plurality of heat-radiating pipes, the gas-phase-side connection section includes a plurality of gas-phase-side connection structures each of which connects the gas-phase refrigerant diffusion section to the third header, which the gas-phase refrigerant flows through, and each of the plurality of the gas-phase-side connection structures connects the gas-phase refrigerant diffusion section to a central region in a longitudinal direction of the third header.
 6. The heat radiation apparatus according to claim 1, further comprising a liquid-phase refrigerant transport section configured to store and transport a liquid-phase refrigerant having passed through the heat-radiating pipe, and a liquid-phase-side connection section configured to connect the liquid-phase refrigerant transport section to the second header, the liquid-phase refrigerant flowing in the liquid-phase-side connection section.
 7. The heat radiation apparatus according to claim 6, wherein a second end of the heat-radiating pipe extends into the second header, the liquid-phase-side connection section includes a second pipe structure, and an extension of a central axis of the second pipe structure is located below the second end.
 8. A phase-change cooling apparatus, comprising: a heat radiation apparatus, the heat radiation apparatus, including a gas-phase refrigerant diffusion section into which a refrigerant in a gas-liquid two-phase state flows, the gas-phase refrigerant diffusion section being filled with a gas-phase refrigerant included in the refrigerant in the gas-liquid two-phase state, a heat-radiating section including a first header, a second header, and a plurality of heat-radiating pipes connecting the first header to the second header, the gas-phase refrigerant flowing through the plurality of heat-radiating pipes, a gas-phase-side connection section configured to connect the gas-phase refrigerant diffusion section to the first header, the gas-phase refrigerant flowing in the gas-phase-side connection section, a liquid-phase refrigerant transport section configured to store and transport a liquid-phase refrigerant having passed through the heat-radiating pipe, and a liquid-phase-side connection section configured to connect the liquid-phase refrigerant transport section to the second header, the liquid-phase refrigerant flowing in the liquid-phase-side connection section; a heat receiving section configured to generate the refrigerant in the gas-liquid two-phase state by receiving heat; a first connection section configured to connect the heat receiving section to the gas-phase refrigerant diffusion section; and a second connection section configured to connect the heat receiving section to the liquid-phase refrigerant transport section.
 9. A method for radiating heat, comprising: receiving a refrigerant in a gas-liquid two-phase state, and generating a diffused gas-phase refrigerant by uniformly diffusing a gas-phase refrigerant included in the refrigerant in the gas-liquid two-phase state; generating a plurality of gas-phase refrigerant flows by making the diffused gas-phase refrigerant branch; and condensing and liquefying each of the plurality of gas-phase refrigerant flows.
 10. The method for radiating heat according to claim 9, wherein the diffused gas-phase refrigerant is made to branch so that a flow distribution of the plurality of gas-phase refrigerant flows may become symmetric.
 11. The heat radiation apparatus according to claim 2, wherein a first end of the heat-radiating pipe extends into the first header, the gas-phase-side connection section includes a first pipe structure, and an extension of a central axis of the first pipe structure is located above the first end.
 12. The heat radiation apparatus according to claim 2, wherein the gas-phase-side connection section includes a first pipe structure, and a central axis of the heat-radiating pipe and a central axis of the first pipe structure have non-parallel relationship on a same plane.
 13. The heat radiation apparatus according to claim 3, wherein the gas-phase-side connection section includes a first pipe structure, and a central axis of the heat-radiating pipe and a central axis of the first pipe structure have non-parallel relationship on a same plane.
 14. The heat radiation apparatus according to claim 2, wherein the heat-radiating section includes a plurality of heat radiators, each of the plurality of heat radiators includes a third header constituting the first header, a fourth header constituting the second header, and the plurality of heat-radiating pipes connecting the third header to the fourth header, and the gas-phase refrigerant flows through the plurality of heat-radiating pipes, the gas-phase-side connection section includes a plurality of gas-phase-side connection structures each of which connects the gas-phase refrigerant diffusion section to the third header, which the gas-phase refrigerant flows through, and each of the plurality of the gas-phase-side connection structures connects the gas-phase refrigerant diffusion section to a central region in a longitudinal direction of the third header.
 15. The heat radiation apparatus according to claim 3, wherein the heat-radiating section includes a plurality of heat radiators, each of the plurality of heat radiators includes a third header constituting the first header, a fourth header constituting the second header, and the plurality of heat-radiating pipes connecting the third header to the fourth header, and the gas-phase refrigerant flows through the plurality of heat-radiating pipes, the gas-phase-side connection section includes a plurality of gas-phase-side connection structures each of which connects the gas-phase refrigerant diffusion section to the third header, which the gas-phase refrigerant flows through, and each of the plurality of the gas-phase-side connection structures connects the gas-phase refrigerant diffusion section to a central region in a longitudinal direction of the third header.
 16. The heat radiation apparatus according to claim 4, wherein the heat-radiating section includes a plurality of heat radiators, each of the plurality of heat radiators includes a third header constituting the first header, a fourth header constituting the second header, and the plurality of heat-radiating pipes connecting the third header to the fourth header, and the gas-phase refrigerant flows through the plurality of heat-radiating pipes, the gas-phase-side connection section includes a plurality of gas-phase-side connection structures each of which connects the gas-phase refrigerant diffusion section to the third header, which the gas-phase refrigerant flows through, and each of the plurality of the gas-phase-side connection structures connects the gas-phase refrigerant diffusion section to a central region in a longitudinal direction of the third header.
 17. The heat radiation apparatus according to claim 2, further comprising a liquid-phase refrigerant transport section configured to store and transport a liquid-phase refrigerant having passed through the heat-radiating pipe, and a liquid-phase-side connection section configured to connect the liquid-phase refrigerant transport section to the second header, the liquid-phase refrigerant flowing in the liquid-phase-side connection section.
 18. The heat radiation apparatus according to claim 3, further comprising a liquid-phase refrigerant transport section configured to store and transport a liquid-phase refrigerant having passed through the heat-radiating pipe, and a liquid-phase-side connection section configured to connect the liquid-phase refrigerant transport section to the second header, the liquid-phase refrigerant flowing in the liquid-phase-side connection section.
 19. The heat radiation apparatus according to claim 4, further comprising a liquid-phase refrigerant transport section configured to store and transport a liquid-phase refrigerant having passed through the heat-radiating pipe, and a liquid-phase-side connection section configured to connect the liquid-phase refrigerant transport section to the second header, the liquid-phase refrigerant flowing in the liquid-phase-side connection section.
 20. The heat radiation apparatus according to claim 5, further comprising a liquid-phase refrigerant transport section configured to store and transport a liquid-phase refrigerant having passed through the heat-radiating pipe, and a liquid-phase-side connection section configured to connect the liquid-phase refrigerant transport section to the second header, the liquid-phase refrigerant flowing in the liquid-phase-side connection section. 